Pocketed gear differential

ABSTRACT

A pocketed gear differential has conventional side gears modified with a plate connectd to the toe and a sleeve arranged about the heel thereof whereby a pocket is formed so that a lubricant entrapped within the meshing gears of the differential cannot readily escape from the sides of the meshing gears and is available to resist rapid movement of the gears to provide a limited slip action.

United States Patent 11 1 1111 3,779,101 Chaput Dec. 18, 1973 [54]POCKETED GEAR DIFFERENTIAL 2,869,399 1/1959 Miles 74/711 3,420,l20l/l969 Burtner 1. 74/7ll [75] lnvemor- Chap, Nashua 2,539,423 1/1951Howard l84/6.l2 x [73] Assignee: Alex Simoneau, Nashua, NH

. Primary E.taminerArthur I. McKeon I22] Flled May 1972 Attorney-Richardl. Seligman [21] Appl. No.: 252,302

[57] ABSTRACT 52 us. (:1. 74/711, l84/6.l2 A pocketed gear differentialhas conventional i e [51 1111. C1. Fl6h 1/44, FOlm 9/10 gears modifiedwith a P t connectd to the toe and a [58] Field of Search 74/711, 710.5,467, Sleeve arranged about the heel thereof whereby 21 74/4 3; 134/ 12;192/61 pocket is formed so that a lubricant entrapped within the meshinggears of the differential cannot readily es- 1 5 References Ci cape fromthe sides of the meshing gears and is avail- UNITED STATES PATENTS ableto resist rapid movement of the gears to provide 1 a limited slipaction. 2 775.I4l 12/1956 Ronnmg 74/7ll 1675,0911 4/1954 Cole 74/467 X11 Claims, 8 Drawing Figures PATENTEBUEE I 81975 SHEET 1 OF 3 BACKGROUNDOF THE INVENTION Automobiles and other automotive vehicles are driventhrough differentials which permit one driven wheel to rotate fasterthan the other driven wheel without strain when turning or when tractionis reduced at one of the driven wheels. The differential supplies equaltorque to both wheels.

A problem can arise where the supplying of an-equal torque to bothdriven wheels is detrimental to operation of th ehvehicle. For example,if one of two driven wheels loses its traction, which often occurs whendriv ing on a slippery surface such as ice, mud, snow or the like. theother wheel will lose torque in proportion to the amount of tractionlost in the one wheel. This will cause the wheel which loses itstraction to spin while the wheel on solid ground remains motionless as,of course, does the. vehicle.

The locking-type differential was developed to eliminate this problem bylocking both output shafts together when high engine power is applied.Therefore, if one wheel loses its traction the other wheel will not loseits torque. Thus, an automotive vehicle with one wheel on a slipperysurface and another on a relatively dry surface can still move forward.

A major problem with the locking-type differential is that when highengine power is applied, thus locking both output shafts, fish-tailingor side-slipping of the vehicle can occur on slippery surfaces. Also,accelerating while turning corners can become a problem since bothoutput shafts lock causing the inner power wheel to turn at the samespeed as the outer wheel. This results in excessive tire wear and, moreimportant, a significant loss of control of the vehicle. Skidding of theinner wheel may cause eratic turns oreven prevent the auto from makingthe turn at all. Furthermore, the locking-type differentials areexpensive, require frequent maintenance and are subject to failure.

US. Pat. No. 3,420,120 describes a differential having a dilitantmaterial such as silicone putty among the differential gears whichpermits the desirable differentialaction under normal conditions whererelative differences in loads and speeds of the output shafts are small,while hopefully preventing the transfer ofall .of the driving torque toone shaft in response to a substantial loss of load on that shaft,Silicone putty exhibits a high resistance to flow under suddenapplication of pressure, but flows under a slow application of pres,-sure. Thus, whensilicone putty is placed among the differential gearsthere is little effect therefrom during normal driving since there isrelatively little difference in speed between the output shafts evenwhen turning. However, when the differential gears tend to rotate at asubstantial speed relative to the gears on the output shafts,thesilicone putty applies a load that resists fast movement of thedifferential gears, thereby limiting the differential action and causingtorqueto be applied to both output shafts.

The drawback to that disclosed in said US. Pat. No. 3,420,120 is thatthe silicone putty has free escape from the sides of the meshing gears,and, thus, there is less material available to resist the speed of thegears. Attempts to remedy this problem are not satisfactory in that theyare relatively expensive, require that major modifications be made tonormal differentials, are relatively complex and decrease thereliability of the simple approach set forth in said US. Pat.No..3,420,l20.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide an improved differential. 1

It is another object of this invention to provide an improveddifferential which is economical, relatively free from maintenance andreliable.

It is a further object of this invention to provide a differential whichwill permit the application of torque to one wheel while another haslost traction and yet not lock both output shafts.

Briefly, an improved differential is provided by substituting pocketedside gears for the conventional side gears at the inner ends of thedriven shafts of a conventional differential, filling the differentialhousing with a high viscosity fluid, preferably, silicone putty, andsealing the differential housing. Pocketed gears which are formed byproviding a plate at the toe of a conventional side gear and a modifiedtruncated cone sleeve at the heel thereof, permit the retention of fluidwithin the gear teeth spaces when the pocketed gear is meshed withdifferential pinions. Since fluid cannot readily es cape from thepocketed gear, the teeth of the pinion will face greater resistance indisplacing the fluid from the pocket into which they enter.

BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other featuresand objects of the invention will become more apparent by reference tothe following description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a pictorial representation of a portion of a conventionaldifferential gearing;

- FIG. 2 is a pictorial representation of a conventional sidei gear ofthe differential of FIG. 1;

FIGS. 3A and 3B are pictorial representations of the additional partswhich are added to the gear of FIG. 2 to make up a pocketed side gearand FIGS. 3C and 3D illustrate an assembled pocketed side gear;

FIG. 4 is a pictorial representation of a portion of a differentialgearing usingthe pocketed side gears of FIGS. 3C and 3D therein; and

FIG. 5 is a pictorial representation of an alternate embodiment of aside gear.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1, there isillustrated thereby a portion of a conventional differential gearingarrangement comprising a pair of side gears 10 and 12 and a number ofdifferential pinion gears only one 14 being shown. The output shafts(not shown) would be connected to side gears l0, 12 in the usual manner.The remainder of the differential has been omitted for clarity as it iswell known to those skilled in the art. In the system described insaidU.S. Pat. No. 3,420,l20 the differential casingis filled withBouncing Putty and the-casing is'sealed to prevent flow of the BouncingPutty" from the casing. As will be apparent from viewing FIG. 1, as anytooth of gear 14 enters the space between two teeth of gear 10 or 12 thematerial (for example, silicone putty) will be forced out of the spaceoffering resistance in proportion to the speed at which the tooth entersthe pocket. However, the displaced siliconeput'ty will be squeezed inpart out of the sides of the gear into the housing and not into thespace from whence the tooth came and, thus, lessing the amount ofsilicone putty available to resist the speed of the differentialpinions.

A conventional side gear 16 is shown in FIG. 2. This side gear ismodified in such a manner that the displaced silicone putty referred toabove will not come out of the side of the gears when meshed but rathermove into the next empty space, that is, the space from which the toothof a differential pinion has come.

Two parts shown in FIGS. 3A and 3B are added to the gear of FIG. 2 tomake up a pocketed gear as shown in FIGS. 3C and 3D. A plate 18 isattached to the toe of gear 16, as, for example, by welding. If aconventional gear is not to be modified but a pocketed gear madeinitially according to the invention then the plate 18 can be cut fromthe same piece of material from which the gear is cut such that theplate 18 will be homogenuous with the gear 16. It becomes apparent thatfluid cannot be pushed out the toe side of the gear by a tooth of apinion since the plate 18 covers the exposed portion of the spacesbetween the teeth of the side gears not meshed with the differentialpinion.

A second part, sleeve 22, is attached, as, for example, by welding tothe heel of a conventional side gear to prevent fluid escaping from theother side of the gear. This piece has a truncated cone surface 24expanding into a cylindrical surface 26.

It is thus seen that when fluid between the teeth of the side gears isdisplaced by a differential pinion entering the space between two teeth,the fluid cannot escape from the sides of the gears and only enter thespace from which the tooth of the pinion has left thereby remainingwithin the meshing gears to resist other teeth of the pinion andproviding the requisite actron.

A portion of the limited slip differential constructed according to theinvention is shown in FIG. 4 and comprises a pair of side gears 28modified as described above with the sleeves 22 and plates 18 which sidegears mesh with differential pinions 14, one only being shown forclarity.

It is noted that the differential has none of the drawbacks of thelocking type differentials and provides significant improvement overthat of said US. Pat. No. 3,420,120 while not increasing the complexityof the mechanism. Only two gears need be modified and then only toattach rigidly thereto two pieces to each gear. There is no addition ofnew moving parts and, thus, no decrease in reliability or increase inmaintenance required.

The differential of FIG. 4 will permit a vehicle to corner withoutspinning its inner power wheel, even while accelerating, greatlyreducing the danger of erratic I turns. Yet should one wheel lose itstraction, as on wet or icy pavement, the other will not lose its torquecompletely as with conventional differentials. On the other hand, itwill not give full torque to both wheels, as with the locking type"differential, but will maintain it in the wheel having traction only inproportion to the RPMs of the spinning wheel. Thereby, the differentialdescribed hereinabove reduces the danger of fishtailing" orside-slipping" and yet provides traction in difficult road conditions,such as slick, wet icy or snowcovered pavement.

The invention will work with pocketed differential gears, spur gears orhelical gears as well as with the pocketed side gears shown anddescribed in detail.

Also, although silicone putty is the preferred fluid, any grease, oil orother lubricant can be employed, and improved slip differential actionwill take place over conventional differentials.

The closer the tolerance between the teeth of the pinion gears and thepocketed teeth of the side gears, the more resistance will be offered tothe pinion teeth in displacing the fluid from the pocket of the sidegears.

The invention will vastly improve the performance of 4-wheel drivevehicles, all terrain type vehicles, as well as industrial off-the-roadvehicles. Popular American-made four-wheel drive vehicles cannot be usedon highways while the four-wheel drive is engaged because front and rearaxles will not stay synchronized, causing excessive strain on the geartrain. Using pocket gear differentials eliminates this problem. A Jeep,for example, would be equipped with three pocketed gear differentials:one in the front axle, one in the rear axle and one in the powertransfer case. Thus, a limited slip or continuous self-adjustment wouldbe allowed between not only the right and left wheels, but also thefront and rear wheels. A Jeep so equipped can, for example, travel atany speed with four-wheel drive engaged on a paved highway withoutdanger of excessive strain in the power-train components.

In an alternate embodiment shown in FIG. 5 conventional side gears areemployed being modified with radial fins 30 therein. The fins will offergreater resistance proportionately to the speed of the gears. Torquewill be distributed more equally to the axle, even if one or the otherwheel encounters less resistance. However, both axles will nevercompletely lock. The radial fins can be used with conventional sidegears or with the pocketed gears previously described.

While I have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthe specification is presented by way of example only and not as alimitation of the scope of this invention as set forth in theaccompanying claims.

I claim:

1. In a differential having a sealed fluid containing housing with apair of side gears and a number of differential pinions therein, whereinthe improvement comprises means substantially enclosing the non-meshingportions of the teeth of said side gears forming a rigid pocket suchthat the fluid entrapped within the meshing gears of the differentialcannot readily escape from the sides thereof.

2. In the differential defined in claim I, said enclosing meansincluding a plate connected to the toe of each of said side gears andextending over a portion of the non-meshing area of the teeth of saidgears, and a sleeve connected to the heel of 'each'of said side gearsand extending over a portion of the non-meshing area of the teeth ofsaid gears.

3. In the differential of claim 2, said fluid being silicone putty.

4. In the differential of claim 2, said sleeve having a truncated conesurface expanding into a cylindrical surface.

5. In the differential of claim 2, said plate being formed integral withits respective side gear.

6. In the differential of claim 2, further including a number of vanesconnected to said plate.

7. In a differential having a sealed fluid containg housing with a pairof side gears and a number of differions and extending over a portion ofthe non-meshing area of the teeth of said pinions.

9. In the differential of claim 8, said fluid being silicone putty.

10. In the differential of claim is, said sleeve having a truncated conesurface expanding into a cylindrical surface.

11. In the differential of claim 8, further including a number of vanesconnected to said plate.

1. In a differential having a sealed fluid containing housing with apair of side gears and a number of differential pinions therein, whereinthe improvement comprises means substantially enclosing the non-meshingportions of the teeth of said side gears forming a rigid pocket suchthat the fluid entrapped within the meshing gears of the differentialcannot readily escape from the sides thereof.
 2. In the differentialdefined in claim 1, said enclosing means including a plate connected tothe toe of each of said side gears and extending over a portion of thenon-meshing area of the teeth of said gears, and a sleeve connected tothe heel of each of said side gears and extending over a portion of thenon-meshing area of the teeth of said gears.
 3. In the differential ofclaim 2, said fluid being silicone putty.
 4. In the differential ofclaim 2, said sleeve having a truncated cone surface expanding into acylindrical surface.
 5. In the differential of claim 2, said plate beingformed integral with its respective side gear.
 6. In the differential ofclaim 2, further including a number of vanes connected to said plate. 7.In a differential having a sealed fluid containg housing with a pair ofside gears and a number of differential pinions therein, wherein theimprovement comprises means substantially enclosing the non-meshingportions of the teeth of said differential pinions forming a rigidpocket such that the fluid entrapped within the meshing gears of thedifferential cannot readily escape from the sides thereof.
 8. In thedifferential defined in claim 7, said enclosing means including a plateconnected to the toe of each of said differential pinions and extendingover a portion of the non-meshing area of the teeth of said pinions, anda sleeve connected to the heel of each of said pinions and extendingover a portion of the non-meshing area of the teeth of said pinions. 9.In the differential of claim 8, said fluid being silicone putty.
 10. Inthe differential of claim 8, said sleeve having a truncated cone surfaceexpanding into a cylindrical surface.
 11. In the differential of claim8, further including a number of vanes connected to said plate.